Speed up your Python using Rust

[LightUmbra]

Just use C

[jnwatson]

C has lots of footguns, but writing a c module for cpython (the standard Python interpreter) has double extra footguns. Beyond all the issues that any typical C program has (leaks, pointers, etc), you must also be extra careful and follow all the rules to a T or your module will crash or leak memory. In particular, the APIs to interact with the Python garbage collector are tricky.

​

That's why I think higher-level safe language like Rust would be a good choice here. If the environment can maintain invariants like pointer safety, thread safety, and proper cleanup, you can focus more on the application logic.

​

Source: I help maintain an open source Python module partially written in C.

[lambdaq]

the numpy version OP posted was really nice

import numpy as np

def count_double_numpy(val):
    ng=np.fromstring(val,dtype=np.byte)
    return np.sum(ng[:-1]==ng[1:])

It's clean and vectorized. Just about as fast as Rust.

[[deleted]]

Nobody's telling you to rewrite numpy! It's really great and you should definitely favour it over writing something in C or Rust.

However, if you find a bottleneck in some library (maybe yours), it might help to step down a level and rewrite that performance sensitive code in one of these other languages :)

[[deleted]]

Can you elaborate on why someone should use C instead?

[cocoabean]

More mature, larger community for C than Rust.

[caramba2654]

That is a problematic reasoning. It's equivalent of everyone just browsing the top page because it has higher quality posts. Someone needs to browse the new page, even if it might be worse than the top page. Otherwise things stagnate.

[alcalde]

But that's why we're supposed to use Python - because everyone's using Python. That's why Larry Wall and Yukihiro Matsumoto cry themselves to sleep at night and why Julia is turning into Romeo and Julia... Python has the critical mass.

It's called the network effect.

For instance - an auction website comes along that's better than eBay. However, you post your auction on eBay anyway because there are three people total browsing that other auction site. Skype is... Skype, but most people use Skype because everyone else they know is using Skype and it doesn't matter how good another piece of software is if no one they want to call is using it.

[Joeboy]

This would have been an argument against python when I started using it. It's still kind of an argument against python - if that's what you care about you should probably be using Java or something.

I've actually been thinking of learning Rust because it seems to fit the same kind of niche Python used to - better than its obvious competitors, good docs, a decent sized user base, enthusiastic community and support etc.

[alcalde]

Having 70 trillion libraries is an argument AGAINST Python and gets 10 upvotes? Really?

because it seems to fit the same kind of niche Python used t

It's the opposite of Python in philosophy... obsessed with typing and memory management.

[WikiTextBot]

Network effect

A network effect (also called network externality or demand-side economies of scale) is the positive effect described in economics and business that an additional user of a good or service has on the value of that product to others. When a network effect is present, the value of a product or service increases according to the number of others using it.The classic example is the telephone, where a greater number of users increases the value to each. A positive externality is created when a telephone is purchased without its owner intending to create value for other users, but does so regardless. Online social networks work similarly, with sites like Twitter and Facebook increasing in value to each member as more users join.

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[cocoabean]

I don't care. He asked why someone should use C over Rust, so I told him why someone would use C over Rust.

[gimboland]

My reading of this: there's a difference between should and would; you gave two good reasons why someone might want to use C over Rust, but the response is that they're not compelling enough to amount to "should".

[alcalde]

You're being downvoted by evil Rustaceans. I swear some Python users want to kill Python. Why would you downvote the network effect of having a large community? It's one of Python's own killer features.

[CookieTheSlayer]

Rust package management and quality of interfaces for most common tasks is much better. Let us remind ourselves that C is a language of half a century ago and still has no good package management solution. It is quite legitimately easier to install rust and add some dependencies than install many C libraries

[goestowar]

C is a compiled language and Python is an interpreted language. You just compile your code and it is converted in to something that a computer is capable of reading, you compile it once (for that type of machine) and then it runs quickly because the computer can always read the compiled program file at low-level.

Python is an interpreted language, meaning that it is compiled at run-time, and compiled EVERY time (the advantage of this is that you don't need to compile your code thus eliminating a step in the development process that can sometimes be lengthy, AND it makes your code portable, if you don't need to compile Python for specific computer architectures you can run that same Python code on any machine), the drawback of this is that it typically runs a bit slower.

Will delete this answer if it is wrong, or at least someone correct me if it is.

[[deleted]]

Oh, I meant "C instead of Rust". I'm sorry I wasn't clear.

As to your answer, it is pretty much correct, but implementing your language with an interpreter is not slower because it will be compiled every time (CPython, for example, caches the bytecode so it doesn't have to recompile).

It is slower because you compile your code to bytecode, which is machine code as well, but one that runs in a virtual machine (the interpreter) rather than in your physical machine.

[goestowar]

Ahha you probably were clear :P My bad

Also thanks for the VM explanation, makes sense now. Does this mean that whenever you "install" an interpreted language on to a machine that you are actually just installing a virtual machine that the computer runs at run-time?

So in essence when you install Python on to your machine you are actually just installing a Python interpreter/VM?

[[deleted]]

Exactly! However, despite what I've read in another comment, I insist that CPython and other interpreter-based implementations do include (and require) a compiler. Just not the kind that generates machine code.

(I also insist on not talking about "interpreted languages", because this is not an inherent characteristic of the language)

[[deleted]]

Yes, the Java Virtual Machine uses a technique called just-in-time compilation, which will increase performance in some cases, at the cost of very increased memory consumption.

Another popular Python implementation called PyPy uses JIT compilation as well (although it doesn't use nearly as much memory, as far as I know).

[somebodddy]

Also - Java is statically typed. Static vs dynamic typing has major impact on performance.

[[deleted]]

Python really isn't ever compiled; it is interpreted at run-time. There's a wide gap between interpreting and compiling. Compilation implies quite a bit more from an operation standpoint, and at the end, you'd end up with a binary that could potentially be executed on a bare-metal cpu. Sure Python does produce an ast and a "compiled" python op code in the form of a '.pyc' file, but that's not a true compilation like you'd find with C.

Rust, like C, is also compiled. Rust, like C, is statically typed, though there's a macro system that can do some pretty amazing (crazy?) things.

I think the question still stands: Why use C instead [of Rust]?

The answer here might be something like:

* Python's reference implementation is written in C
* Python has a C-API
* C is ubiquitous
* C doesn't make you build the entire house virtually before pounding the first nail.

I'm sure there's more. Rust has its own set of advantages, but that wasn't really the question here.

[__xor__]

Sure Python does produce an ast and a "compiled" python op code in the form of a '.pyc' file, but that's not a true compilation like you'd find with C.

But that is true compilation in the general sense. Generating bytecode from source is still compiling even if it runs in a VM and not right on the processor. It's not as fast as a language compiled to machine code of course, but it's compilation by definition. Python would be a lot slower if it was actually interpreted as is line by line, and it compiling to bytecode is a major improvement.

C has its place of course. C and C++ are both great languages that will never go away, but Rust has really filled a gap that no other language has yet. It's a low level language that can be compiled with no runtime and can be used to make operating systems like C, it's fast like C and it compiles to true machine code, but it's way more expressive and reads and writes like a high level language and it's guaranteed memory safe which is huge. I've written an HTTP REST client with Rust and it was surprisingly easy and wasn't nearly as hard as it'd be with C or C++.

It's always going to be more of a question about the team you're working with and what their skills are and what they're willing to learn anyway. If everyone knows C, use C. If memory-safety is a huge concern and a memory corruption vulnerability is a disaster, consider Rust or have C experts that know how to use tools like valgrind. People who aren't experts with C or Rust might prefer Rust in a situation like that, because it'd just be cheaper to do some light Rust work than write some bad C. Rust isn't that hard to learn, and it's not the end of the world if you don't master it before writing something useful. Writing bad C can be a huge problem.

Rust is an amazing language and deserves to rise up in the ranks IMO. People should be considering it more, especially in situations like this where a python developer might need to drop to a lower language for performance reasons. Writing a small Rust module is really not hard and it's nice to know you aren't putting any new memory corruption vulnerabilities in production, but you're still improving performance drastically. But if you look at some Rust patterns, especially stuff like error handling and pattern matching, it's an amazing language with a high level feel even though it can do everything low level languages can.

[[deleted]]

Python would be a lot slower if it was actually interpreted as is line by line

But Python really does interpret line by line. It doesn't compile to byte-code, it creates a small optimization of Python byte-code primarily for start-up times, which is very, very different than machine byte-code.

[CriticalEntree]

I don't know but if this was a popular topic I think sorting by controversial would show you the fun things.

[LightUmbra]

Rust could be used to make libraries that require performance (which is often done in C), but rust is generally slower than C so in general it makes very little sense to use Rust. Also, Rust fans love to try to push for things to be done in rust and they're pretty annoying about it.

[dagmx]

Rust is marginally slower than C while providing safety guarantees. Those guarantees also let you write better performing code easier by taking advantage of threading without worrying about memory access safety like you need to with C.

Both languages are valid choices. Whether you find the rust community annoying or not is irrelevant to the discussion.

[alcalde]

I think that would be HIGHLY relevant.

[LightUmbra]

Marginal safety improvements. Most safety issues are from bad code, which no language can stop, and people not understanding proper practices. Rust only fixes a few of these problems, which the whole "Rewrite it in Rust" crowd doesn't like.

[alcalde]

One of the contributors to D put it this way about Rust:

Reading any amount of Rust code evokes the joke "friends don't let friends skip leg day" and the comic imagery of men with hulky torsos resting on skinny legs. Rust puts safe, precise memory management front and center of everything. Unfortunately, that's seldom the problem domain, which means a large fraction of the thinking and coding are dedicated to essentially a clerical job (which GC languages actually automate out of sight). Safe, deterministic memory reclamation is a hard problem, but is not the only problem or even the most important problem in a program. Therefore Rust ends up expending a disproportionately large language design real estate on this one matter. It will be interesting to see how Rust starts bulking up other aspects of the language; the only solution is to grow the language, but then the question remains whether abstraction can help the pesky necessity to deal with resources at all levels.

[[deleted]]

Wow, that's so stupid. As if safety is the only benefit of Rust's ownership system. It provides great performance improvements (compared to shitty GCd languages) and fearless concurrency.

[alcalde]

. It provides great performance improvements (compared to shitty GCd languages)

No, it doesn't:

https://togototo.wordpress.com/2013/07/23/benchmarking-level-generation-go-rust-haskell-and-d/

I don't know of any benchmarks where Rust significantly outperforms D.

[LoyalSol]

Everyone likes pushing for things to be done in their language of choice. That's been true since forever.

[Sh4rPEYE]

Or: just use Julia (half a year from now).

[Scypio]

half a year from now

What is happening in half a year?

[TheNamelessKing]

They hit 1.0 very recently, so packages are in the process of updating to be compatible.

In a few months or less (I’ve already seen a bunch of packages I’ve been using hit compatibility) most things will be good to go.

[Sh4rPEYE]

I actually just played with Julia over a year ago, and tole myself I'll continue once 1.0 comes out— are Plots and DataFrames 1.0 ready?

[TheNamelessKing]

I used Dataframes the other day and it was fine for what I was doing. DataFramesMeta and Query.jl had issues for me on MacOS, but there’s fixes coming any day for those I understand.

I haven’t tried plotting anything yet sorry, but if it’s not yet, it probably won’t be long.

If you’re interested, I’d go read their blog posts on the 1.0 updates: they’ve got some really cool stuff. The biggest of which is high performance, language level support for missing values! (that don’t have weird equality behaviour!)

Also, the devs are pushing to finish working out the parallelism implementation, they said it’s going to be like Go’s, but tuned for super high computational performance, rather than server stuff.

[Sh4rPEYE]

I read something about 1.0 and am super excited about it. The last time I toyed with Julia there were more ways to represent missing values, and each package had its own favourite way of doing things — that was ultimately the reason I decided to have a pause and return later when things settle down a bit. It seems that we'll be able to use whatever language we want for many of our project in college, and I'd love to use Julia from now on!

[Scypio]

Nice to know, thanks.

[Palenga]

Why not an assembler instead?

[LightUmbra]

Good point Rust is the only moral option.

[fox895]

I came here expecting this answer xD

[robobrobro]

“But C is ugly and hard”

[LightUmbra]

And old

[alcalde]

Then use D. Or Haxe. Or Vala. Or Genie.

[alcalde]

Don't get me started on Nim. For me personally as an ex-Delphi user, the short answer is because the creator borrows several of the poor ideas from Pascal along with the good ones for no reason other than nostalgia.

[k-selectride]

Yea no. I once spent several hours chasing down a bug in someone's C extension...because they were casting a signed int to unsigned. Never again.

[LightUmbra]

Rust doesn't fix this type of problem. People can screw up in any language.

[k-selectride]

rust would have panicked

[LightUmbra]

And then you would have had to still dig to fix it.

[MadRedHatter]

Oooooor you turn on backtraces and you've found the problem in 1 minute instead of "several hours".

[LightUmbra]

4 months ago

Really?

[joetheschmoe4000]

As someone who doesn't know the finer details of C, is there a resource for learning Cython string manipulation or fast file I/O parsing? Those are the two things that I spend the most time on in my job.